1. Field of the Invention
This invention relates to an image data generating method for generating image data of an image recorded on a holographic stereogram. The invention also relates to a video data converting method for processing image data of plural images inclusive of the parallax information with pre-set video data conversion processing for generating image data of an image recorded on a holographic stereogram.
2. Description of the Related Art
A holographic stereogram is prepared by sequentially imaging an object from different viewing points for producing plural images as original images and by sequentially recording the images as elementary hologram (hologram elements) in the form of dots or strips.
For producing a holographic stereogram having the parallax information only in the horizontal direction, an object 100 is sequentially imaged from different viewing points in the horizontal direction for producing plural images 101 having the parallax information in the horizontal direction, as shown in FIG. 1. After forming these images into image data, the latter is processed by a computer by pre-set image data conversion processing for generating image data of an image 102 to be recorded on the holographic stereogram. Each image 102 derived from the image data processed with image data conversion processing is sequentially recorded on end in the horizontal direction as a strip-like element hologram on a recording medium for hologram 103. This produces a holographic stereogram having the parallax information in the horizontal direction.
With this holographic stereogram, the information of plural images obtained on sequentially imaging an object from plural different viewing points is sequentially recorded in succession in the horizontal direction as a hologram of plural strip-like elements, so that, if a viewer views the holographic stereogram with both his or her eyes, the two-dimensional images as viewed by the left and right eyes of the viewer are slightly different from each other. Thus the user feels parallax so that a three-dimensional image is reproduced.
Meanwhile, if is desired for a reproduced image of a holographic stereogram to be viewed by the viewer as a spontaneous three-dimensional image, it is necessary to lay in store an extremely large number of images from which the holographic stereogram is derived.
Specifically, even with a holographic stereogram having the parallax information only in the horizontal direction, at least hundreds of original images are required, depending on the size or resolution of the holographic stereogram, for generating a sole holographic stereogram.
Thus, since the holographic stereogram handles voluminous image data, the conventional holographic stereogram formulating system stores image data of original images in a large-capacity external storage device, such as a hard disc drive, and pre-set image data conversion processing is performed on the image data for generating the image data of images recorded on the holographic stereogram.
Meanwhile, for producing the string of parallax images, as original images of the holographic stereogram, an imaging device 111, directed to an object 110, is moved by translational movement as indicated by arrow B1 in FIG. 2, while the imaging device 111 is maintained in the same orientation, and an object 110 is imaged a large number of times from this position. That is, the imaging device 111, directed to the object 110, is moved by transnational movement from a position in which the object 110 enters an imaging range by the imaging device 111 to a position in which the object 110 exits the imaging range by the imaging device 111. During this time, a large number of images are shot.
However, if, with the imaging method, the object 110 is large in size, the imaging device 110 needs to be moved a long distance for imaging the object in its entirety, with the result that the system for producing the string of parallax images is increased in size.
In the above imaging operation, an image angle .theta.v of the imaging device 111, which is reflected in the angle of visibility in the horizontal direction of the holographic stereogram, needs to be set to a sufficiently large value. However, for setting the image angle .theta.v of the imaging device 111 to a large value, a wide angle lens needs to be used, thus raising the cost of the imaging device 111. Moreover, if the image is shot using a wide angle lens with the image angle .theta.v of the imaging device 111 set to a large value, the image tends to be distorted, thus tending to deteriorate the image quality of the holographic stereogram.
In addition, if the string of the parallax images is imaged as described above, many unneeded portions devoid of an image of the object 110 are contained in the string of the parallax images. In particular, the images towards the leading end and the trailing end of the string of the parallax images contain image portions only towards the edge portions thereof, with the main portions thereof being unneeded portions devoid of the image of the object 110. Thus, if image data is produced from the string of parallax images, a large number of unneeded image data are contained, thus counteracting effective data utilization.
Alternatively, the string of parallax images, as original images of the holographic stereogram, may also be obtained by setting the object 110 on a turntable 112, with the imaging device 110 being fixed, and by rotating the turntable 112 a pre-set angle each time the object 110 is imaged, as indicated by arrow B2 in FIG. 3, for shooting plural images with different viewing angles.
As compared to the method of moving the imaging device 111 by translational movement, as shown in FIG. 2, the above-described imaging method has an advantage that the overall size of the imaging system for the string of parallax images can be reduced even if the object 110 has an increased size. Also, a sufficient angle of visibility in the horizontal direction can be assured by rotating the object 110 even if the image angle .theta.v is small. Moreover, since the object 110 is positioned at all times on the front side of the imaging device 111 even if the turntable 112 is rotated, the parallax images of the string are substantially free of unneeded portions devoid of images of the object 110. Thus, if the image data is generated from this string of parallax images, unneeded image data are scarcely contained, thus meritoriously assuring effective data utilization.
Since the conventional holographic stereogram is prepared from viewing points at the shooting time, the holographic stereogram produced on the basis of the string of parallax images obtained on rotating the object 110 as described above is arcuately shaped in meeting with the viewing points at the shooting time. As a matter of course, the holographic stereogram is desirably planar in shape in consideration that the holographic stereogram producing system is used as a printer for outputting a hard copy capable of generating a three-dimensional image.
On the other hand, in formulating a holographic stereogram, since voluminous image data needs to be processed with an image data converting operation and subsequently a large number of images needs to be recorded sequentially as hologram elements, it takes considerable time to produce a holographic stereogram.
However, if it is envisaged to implement the holographic stereogram producing system as a printer device for outputting a hard copy capable of producing a three-dimensional image, it is desirable to reduce the time which elapses since inputting of images as original images of the holographic stereogram until completion of the holographic stereogram.
For example, the image data conversion processing of generating image data of images recorded on the holographic stereogram from image data of the original images is extremely time-consuming, and hence it is desired to speed up the image data conversion processing operations.
In particular, in image data conversion processing, the data processing volume is increased with improved quality of the three-dimensional image to be recorded on the holographic stereogram. That is, if it is attempted to raise the resolution, image data is increased in quantity, thus increasing the processing time involved in image data conversion. On the other hand, if color correction is envisaged for improving color reproducibility, the processing time involved in image data conversion processing is increased. The result is that the processing speed in the image data conversion processing needs to be raised as the higher image quality is aimed at.